Remove all wayland-server.h includes

The documentation for wayland-server.h says:

> Use of this header file is discouraged. Prefer including
> wayland-server-core.h instead, which does not include the server protocol
> header and as such only defines the library PI, excluding the deprecated API
> below.

Replacing wayland-server.h with wayland-server-core.h allows us to drop the
WL_HIDE_DEPRECATED declaration.

backend/session/direct-freebsd.c

@@ -13,7 +13,7 @@
 #include <sys/types.h>
 #include <termios.h>
 #include <unistd.h>
-#include <wayland-server.h>
+#include <wayland-server-core.h>
 #include <wlr/backend/session/interface.h>
 #include <wlr/util/log.h>
 #include <xf86drm.h>

backend/session/direct.c

@@ -14,7 +14,7 @@
 #include <sys/stat.h>
 #include <sys/sysmacros.h>
 #include <unistd.h>
-#include <wayland-server.h>
+#include <wayland-server-core.h>
 #include <wlr/backend/session/interface.h>
 #include <wlr/util/log.h>
 #include "backend/session/direct-ipc.h"

backend/session/logind.c

@@ -9,7 +9,7 @@
 #include <sys/stat.h>
 #include <sys/sysmacros.h>
 #include <unistd.h>
-#include <wayland-server.h>
+#include <wayland-server-core.h>
 #include <wlr/backend/session/interface.h>
 #include <wlr/config.h>
 #include <wlr/util/log.h>

backend/session/noop.c

@@ -3,7 +3,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <unistd.h>
-#include <wayland-server.h>
+#include <wayland-server-core.h>
 #include <wlr/backend/session/interface.h>
 #include <wlr/util/log.h>
 #include "util/signal.h"

backend/session/session.c

@@ -6,7 +6,7 @@
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <wayland-server.h>
+#include <wayland-server-core.h>
 #include <wlr/backend/session.h>
 #include <wlr/backend/session/interface.h>
 #include <wlr/config.h>